DOCSLIB.ORG

Lamellar Organization of Pigments in Chlorosomes, the Light Harvesting Complexes of Green Photosynthetic Bacteria

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lamellar Organization of Pigments in Chlorosomes, the Light Harvesting Complexes of Green Photosynthetic Bacteria View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Biophysical Journal Volume 87 August 2004 1165–1172 1165 Lamellar Organization of Pigments in Chlorosomes, the Light Harvesting Complexes of Green Photosynthetic Bacteria J. Psˇencˇ´ık,*T.P.Ikonen,y P. Laurinma¨ki,z M. C. Merckel,§ S. J. Butcher,z R. E. Serimaa,y and R. Tumaz *Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic; and yDivision of X-ray Physics, Department of Physical Sciences, zInstitute of Biotechnology and Department of Biological and Environmental Science, and §Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, Helsinki, Finland ABSTRACT Chlorosomes of green photosynthetic bacteria constitute the most efficient light harvesting complexes found in nature. In addition, the chlorosome is the only known photosynthetic system where the majority of pigments (BChl) is not organized in pigment-protein complexes but instead is assembled into aggregates. Because of the unusual organization, the chlorosome structure has not been resolved and only models, in which BChl pigments were organized into large rods, were proposed on the basis of freeze-fracture electron microscopy and spectroscopic constraints. We have obtained the first high- resolution images of chlorosomes from the green sulfur bacterium Chlorobium tepidum by cryoelectron microscopy. Cryoelectron microscopy images revealed dense striations ;20 A˚ apart. X-ray scattering from chlorosomes exhibited a feature with the same ;20 A˚ spacing. No evidence for the rod models was obtained. The observed spacing and tilt-series cryoelectron microscopy projections are compatible with a lamellar model, in which BChl molecules aggregate into semicrystalline lateral arrays. The diffraction data further indicate that arrays are built from BChl dimers. The arrays form undulating lamellae, which, in turn, are held together by interdigitated esterifying alcohol tails, carotenoids, and lipids. The lamellar model is consistent with earlier spectroscopic data and provides insight into chlorosome self-assembly. INTRODUCTION Photosynthesis is the ultimate source of energy for most sions 1500 3 500 3 200 A˚ ,1A˚ ¼ 0.1 nm) and the large current life forms, including humans. The first step in number of pigment molecules inside. A typical chlorosome utilization of solar energy is photon capture by a light- contains on the order of 105 BChl molecules (Montano et al., harvesting system (antenna). Typically, the antennae are 2003) (BChl c, d, e, depending on the species) in the form of composed of pigment-protein complexes, in which the aggregates. The aggregation modulates the optical properties protein framework determines pigment orientations and of the BChls and results in fast energy transfer rates optical properties, and ensures efficient flow of excitation (Prokhorenko et al., 2000; Psencik et al., 2003, and energy to the photosynthetic reaction center. The only references therein), which are a prerequisite for the light- known exception is the chlorosome. Chlorosomes are large harvesting efficiency. enclosures of BChl aggregates, which are organized by Chlorosomes were first reported in 1963 and their pigment-pigment rather than pigment-protein interactions, structure was subsequently characterized by electron mi- and are attached to the inner side of the cytoplasmic croscopy (Cohen-Bazire et al., 1964). The electron micro- membrane of green photosynthetic bacteria (Blankenship graphs of Cohen-Bazire and co-workers revealed 12–20 A˚ et al., 1995; Frigaard et al., 2003). Two bacterial families, the wide striations, arrayed more or less parallel to the long axis green sulfur and the green nonsulfur bacteria, belong to this of the chlorosome, but no interpretation was given. Later, group and are only distantly related, but use chlorosomes as this observation was overshadowed by freeze-fracture the main light harvesting system. The green sulfur bacteria electron microscopy study (Staehelin et al., 1978, 1980), in are able to survive at the lowest light conditions of all known which micrographs of chlorosome interiors were interpreted photosynthetic organisms (Overmann et al., 1992; Frigaard in terms of rod-like elements with a diameter of 50 A˚ et al., 2003). In effect, the chlorosome is the most efficient (nonsulfur bacteria) or 100 A˚ (sulfur bacteria). This antenna known. The efficiency is in part due to the large size interpretation was reinforced by freeze-fracture (Oelze and of the chlorosome (ellipsoidal particle with typical dimen- Golecki, 1995) and disruption (Wullink and van Bruggen, 1988) studies and became the basis for all subsequent chlorosome models. Perhaps because of the large size and unusual organization, no crystals of chlorosomes or ag- Submitted January 21, 2004, and accepted for publication May 20, 2004. gregated BChls have been obtained, and the chlorosome Address reprint requests to R. Tuma, Institute of Biotechnology, remains the last known light-harvesting complex for which Viikinkaari 1, PL 65, University of Helsinki, FIN-00014, Helsinki, Finland. Tel.: 358-9-19159577; Fax: 358-9-19159930; E-mail: roman.tuma@ no high-resolution structural information is available. helsinki.fi. Several models for the organization of BChl aggregates Abbreviations used: BChl, Bacteriochlorophyll; Chl., chlorobium; EM, into rod-like elements were proposed (Holzwarth and cryoelectron microscopy; OD, optical density (cmÿ1); SAXS, small angle Schaffner, 1994; Nozawa et al., 1994; Blankenship et al., x-ray scattering; WAXS, wide angle x-ray scattering. Ó 2004 by the Biophysical Society 0006-3495/04/08/1165/08 $2.00 doi: 10.1529/biophysj.104.040956 1166 Psˇencˇ´ıketal. 1995; van Rossum et al., 2001). These models can be another round of density-gradient centrifugation. The density and the optical classified into two principal groups based on the asymmetric absorption spectrum of the resulting chlorosomes were measured to assure repeating unit: 1), parallel-chain model with BChl monomer sample integrity. The absorption spectra were measured before and after each experiment to ensure that no degradation occurred during exposure to as the building block (Holzwarth and Schaffner, 1994; x rays or during the handling required for EM sample preparation. Balaban et al., 1995; Chiefari et al., 1995; van Rossum et al., 2001); and 2), antiparallel double-chain model with an antiparallel so-called ‘‘piggy-back’’ BChl dimer as a building Electron microscopy block (Smith et al., 1986; Nozawa et al., 1994; Umetsu et al., Small drops (10 ml) of fresh chlorosome solution (OD ;80 per cm at 748 1999; Wang et al., 1999a; Umetsu et al., 2002). The terms nm) were dialyzed for 1 min using Millipore 0.025 mm pore membrane parallel and antiparallel refer to the mutual orientation of the (Millipore, Billerica, MA), against 5 mM Tris, pH 8. Protein-A gold (50 A˚ , Q transition dipoles. In all these models, short-range order Dept. of Cell Biology, University of Utrecht) was added to chlorosome y solutions before dialysis as fiducial markers for tilt experiments. Grid was based on the results of NMR and optical spectroscopy preparation and vitrification was accomplished by the guillotine method of (Smith et al., 1986; Hildebrandt et al., 1991; Holzwarth and Dubochet et al. (1988) in liquid-nitrogen cooled ethane. The vitrified Schaffner, 1994; Nozawa et al., 1994; Balaban et al., 1995; samples were examined in a Tecnai F20 transmission electron microscope Chiefari et al., 1995; Umetsu et al., 1999, 2002; Wang et al., using an Oxford CT3500 cryo-holder (EM Unit, Institute of Biotechnology, 3 1999a; Mizoguchi et al., 2000; van Rossum et al., 2001). University of Helsinki). Micrographs were recorded at 200 kV, 50,000 magnification, 0.8–3.2 mm underfocus, on Kodak S0163 film using low Most notably, the long-range order followed from constrain- dose. Images free from astigmatism and drift were scanned at 7 mm step size ing the models to resemble the rod-like elements of Staehelin (1.4 A˚ per pixel) using a Zeiss Photoscan TD scanner. The defocus of the et al. (1978, 1980). Furthermore, none of these models has scanned micrographs was calculated using the program CTFFIND3 provided insight into chlorosome assembly. (Grigorieff, 1998). Individual chlorosomes were boxed (1000 3 1000 In addition to BChl aggregates, chlorosomes contain BChl pixels) from the original images and subregions containing the fine structure were selected (area of 125 3 125 pixels). The subregions were padded to a, carotenoids, quinones, lipids, and proteins. Lipids pre- 2048 3 2048 array with the average image intensity, and power spectra were sumably form an enveloping monolayer of the chlorosome calculated. and the coupling to the cytoplasmic membrane is achieved via a BChl a-containing protein baseplate (Blankenship et al., 1995; Frigaard et al., 2003). Proteins constitute a minor X-ray scattering component and are thought to reside in the chlorosome Samples for x-ray scattering were prepared by rapid dialysis against 1 mM baseplate and envelope (Blankenship et al., 1995; Frigaard Tris, pH 8, followed by controlled concentration under low vacuum to avoid et al., 2003). complete drying and salt crystallization. The concentrated but fluid sample (OD ;2000 per cm at 748 nm) was loaded into a steel-framed sample cell Here we present the first EM images of intact Chlorobium (thickness 1 mm) sealed with two 13 mm Capton windows. The ÿ tepidum chlorosomes embedded in vitreous ice. EM was measurements in the q-range of 0.1–2.5 A˚ 1 (q ¼ 4 3 p sin(q/2)/l, where complemented by solution SAXS and WAXS. Both the q is the scattering angle and l is the wavelength) were made on the in-house high-resolution EM images and SAXS revealed fine internal x-ray scattering apparatus in Division of X-ray Physics, University of structure with spacing of ;20 A˚ , which can be explained by Helsinki. The quasi-monochromatic x rays (Cu Ka) scattered from the sample were detected with a two-dimensional proportional counter. The a simple lamellar organization of pigment molecules.
Load more

Recommended publications
  • Chromatic Acclimation and Population Dynamics of Green Sulfur Bacteria Grown with Spectrally Tailored Light
    Chromatic acclimation and population dynamics of green sulfur bacteria grown with spectrally tailored light Semion K. Saikin,a,† Yadana Khin,b Joonsuk Huh,a Moataz Hannout,c Yaya Wang,b Farrokh Zare,b Alán Aspuru-Guzik,a Joseph Kuo-Hsiang Tangb,* a Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138 USA; b School of Chemistry and Biochemistry, Clark University, Worcester, MA 01610-1477 USA, c Department of Physics, Clark University, Worcester, MA 01610-1477 USA To whom correspondence should be addressed: †E-mail: [email protected], Tel: 1-617-496-8221, Fax: 1-617-496-9411 *E-mail: [email protected],Tel: 1-614-316-7886, Fax: 1-508-793-8861 Keywords: photosynthesis, chromatic acclimation, energy transfer, light-harvesting complex, chlorosome, green sulfur bacteria Living organisms have to adjust to their surrounding in order to survive in stressful conditions. We study this mechanism in one of most primitive creatures – photosynthetic green sulfur bacteria. These bacteria absorb photons very efficiently using the chlorosome antenna complexes and perform photosynthesis in extreme low-light environments. How the chlorosomes in green sulfur bacteria are acclimated to the stressful light conditions, for instance, if the spectrum of light is not optimal for absorption, is unknown. Studying Chlorobaculum tepidum cultures with far-red to near-infrared light-emitting diodes, we found that these bacteria react to changes in energy flow by regulating the amount of light- absorbing pigments and the size of the chlorosomes. Surprisingly, our results indicate that the bacteria can survive in near-infrared lights capturing low-frequency photons by the intermediate units of the light-harvesting complex.
    [Show full text]
  • Chapter 3 the Title and Subtitle of This Chapter Convey a Dual Meaning
    3.1. Introduction Chapter 3 The title and subtitle of this chapter convey a dual meaning. At first reading, the subtitle Photosynthetic Reaction might seem to indicate that the topic of the structure, function and organization of Centers: photosynthetic reaction centers is So little time, so much to do exceedingly complex and that there is simply insufficient time or space in this brief article to cover the details. While this is John H. Golbeck certainly the case, the subtitle is Department of Biochemistry additionally meant to convey the idea that there is precious little time after the and absorption of a photon to accomplish the Molecular Biology task of preserving the energy in the form of The Pennsylvania State University stable charge separation. University Park, PA 16802 USA The difficulty is there exists a fundamental physical limitation in the amount of time available so that a photochemically induced excited state can be utilized before the energy is invariably wasted. Indeed, the entire design philosophy of biological reaction centers is centered on overcoming this physical, rather than chemical or biological, limitation. In this chapter, I will outline the problem of conserving the free energy of light-induced charge separation by focusing on the following topics: 3.2. Definition of the problem: the need to stabilize a charge-separated state. 3.3. The bacterial reaction center: how the cofactors and proteins cope with this problem in a model system. 3.4. Review of Marcus theory: what governs the rate of electron transfer in proteins? 3.5. Photosystem II: a variation on a theme of the bacterial reaction center.
    [Show full text]
  • 1 Temperature and Carbon Assimilation Regulate The
    Temperature and Carbon Assimilation Regulate the Chlorosome Biogenesis in Green Sulfur Bacteria Joseph Kuo-Hsiang Tang1,*, Semion K. Saikin2, Sai Venkatesh Pingali3, Miriam M. Enriquez4, Joonsuk Huh2, Harry A. Frank4, Volker S. Urban3, Alán Aspuru-Guzik2 1School of Chemistry and Biochemistry, Clark University, Worcester, MA 01610 USA, 2Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138 USA, 3Center for Structural Molecular Biology, Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA, 4Department of Chemistry, University of Connecticut, Storrs, CT 06269 USA Running title: Metabolic regulation of chlorosome *To whom correspondence should be addressed: Tel: 1-614-316-7886, Fax: 1-508-793-8861, E-mail: [email protected] Abstract Green photosynthetic bacteria adjust the structure and functionality of the chlorosome – the light absorbing antenna complex – in response to environmental stress factors. The chlorosome is a natural self-assembled aggregate of bacteriochlorophyll (BChl) molecules. In this study we report the regulation of the biogenesis of the Chlorobaculum tepidum chlorosome by carbon assimilation in conjunction with temperature changes. Our studies indicate that the carbon source and thermal stress culture of Cba. tepidum grows slower and incorporates less BChl c in the chlorosome. Compared with the chlorosome from other cultural conditions we investigated, the chlorosome from the carbon source and thermal stress culture displays: (a) smaller cross- sectional radius and overall size; (b) simplified BChl c homologues with smaller side chains; (c) blue-shifted Qy absorption maxima and (d) a sigmoid-shaped circular dichroism (CD) spectra. Using a theoretical model we analyze how the observed spectral modifications can be associated with structural changes of BChl aggregates inside the chlorosome.
    [Show full text]
  • Probing the Spatial Organization of Bacteriochlorophyll C by Solid
    Article pubs.acs.org/biochemistry Probing the Spatial Organization of Bacteriochlorophyll c by Solid- State Nuclear Magnetic Resonance † § ‡ § † † Shih-Chi Luo, Yadana Khin, Shing-Jong Huang, Yanshen Yang, Tsai-yi Hou, Yuan-Chung Cheng, † ∥ ∥ ∥ § Hao Ming Chen, Yi-Ying Chin, Chien-Te Chen, Hong-Ji Lin, Joseph Kuo-Hsiang Tang,*, † and Jerry Chun Chung Chan*, † ‡ Department of Chemistry and Instrumentation Center, National Taiwan University, Taipei 10617, Taiwan § Department of Chemistry and Biochemistry, Clark University, Worcester, Massachusetts 01610, United States, ∥ National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan *S Supporting Information ABSTRACT: Green sulfur bacteria, which live in extremely low-light environ- ments, use chlorosomes to harvest light. A chlorosome is the most efficient, and arguably the simplest, light-harvesting antenna complex, which contains hundreds of thousands of densely packed bacteriochlorophylls (BChls). To harvest light efficiently, BChls in a chlorosome form supramolecular aggregates; thus, it is of great interest to determine the organization of the BChls in a chlorosome. In this study, we conducted a 13C solid-state nuclear magnetic resonance and Mg K-edge X-ray absorption analysis of chlorosomes from wild-type Chlorobaculum tepidum. The X-ray absorption results indicated that the coordination number of the Mg in the chlorosome must be >4, providing evidence that electrostatic interactions formed between the Mg of a BChl and the carbonyl group or the hydroxyl group of the neighboring BChl molecule. According to the intermolecular distance constraints obtained on the basis of 13C homonuclear dipolar correlation spectroscopy, we determined that the molecular assembly of BChls is dimer-based and that the hydrogen bonds among the BChls are less extensive than commonly presumed because of the twist in the orientation of the BChl dimers.
    [Show full text]
  • The Chlorosome: a Prototype for Efficient Light Harvesting In
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Wageningen University & Research Publications Photosynth Res DOI 10.1007/s11120-010-9533-0 REVIEW The chlorosome: a prototype for efficient light harvesting in photosynthesis Gert T. Oostergetel • Herbert van Amerongen • Egbert J. Boekema Received: 24 November 2009 / Accepted: 16 January 2010 Ó The Author(s) 2010. This article is published with open access at Springerlink.com Abstract Three phyla of bacteria include phototrophs Introduction that contain unique antenna systems, chlorosomes, as the principal light-harvesting apparatus. Chlorosomes are the Since the earliest photosynthetic organisms developed largest known supramolecular antenna systems and contain reaction centres, additional peripheral antenna systems hundreds of thousands of BChl c/d/e molecules enclosed by have evolved for light harvesting. In these light-harvesting a single membrane leaflet and a baseplate. The BChl pig- systems, dozens, hundreds or even thousands of (bacte- ments are organized via self-assembly and do not require rio)chlorophylls can funnel their excitation energy towards proteins to provide a scaffold for efficient light harvesting. reaction centres for charge separation. The green photo- Their excitation energy flows via a small protein, CsmA synthetic bacteria are anoxygenic phototrophs that contain embedded in the baseplate to the photosynthetic reaction unique antenna complexes, known as chlorosomes (Blan- centres. Chlorosomes allow for photosynthesis at very low kenship and Matsuura 2003). A chlorosome is actually a light intensities by ultra-rapid transfer of excitations to kind of organelle. In addition to the green sulphur bacteria reaction centres and enable organisms with chlorosomes to (phylum Chlorobi), they are also present in some fila- live at extraordinarily low light intensities under which no mentous anoxygenic phototrophs of the phylum Chloroflexi other phototrophic organisms can grow.
    [Show full text]
  • Superradiance of Bacteriochlorophyll C Aggregates in Chlorosomes Of
    www.nature.com/scientificreports OPEN Superradiance of bacteriochlorophyll c aggregates in chlorosomes of green photosynthetic bacteria Tomáš Malina1, Rob Koehorst2,3, David Bína4,5, Jakub Pšenčík1* & Herbert van Amerongen2,3 Chlorosomes are the main light-harvesting complexes of green photosynthetic bacteria that are adapted to a phototrophic life at low-light conditions. They contain a large number of bacteriochlorophyll c, d, or e molecules organized in self-assembling aggregates. Tight packing of the pigments results in strong excitonic interactions between the monomers, which leads to a redshift of the absorption spectra and excitation delocalization. Due to the large amount of disorder present in chlorosomes, the extent of delocalization is limited and further decreases in time after excitation. In this work we address the question whether the excitonic interactions between the bacteriochlorophyll c molecules are strong enough to maintain some extent of delocalization even after exciton relaxation. That would manifest itself by collective spontaneous emission, so-called superradiance. We show that despite a very low fuorescence quantum yield and short excited state lifetime, both caused by the aggregation, chlorosomes indeed exhibit superradiance. The emission occurs from states delocalized over at least two molecules. In other words, the dipole strength of the emissive states is larger than for a bacteriochlorophyll c monomer. This represents an important functional mechanism increasing the probability of excitation energy transfer that is vital at low-light conditions. Similar behaviour was observed also in one type of artifcial aggregates, and this may be benefcial for their potential use in artifcial photosynthesis. Green sulfur bacteria are capable to live phototrophically at extremely low-light conditions 1,2.
    [Show full text]
  • Strong Coupling Between Chlorosomes of Photosynthetic Bacteria and a Confined Optical Cavity Mode
    ARTICLE Received 2 Jul 2014 | Accepted 14 Oct 2014 | Published 28 Nov 2014 DOI: 10.1038/ncomms6561 Strong coupling between chlorosomes of photosynthetic bacteria and a confined optical cavity mode David M. Coles1, Yanshen Yang2, Yaya Wang2, Richard T. Grant3, Robert A. Taylor4, Semion K. Saikin5,6, Ala´n Aspuru-Guzik5, David G. Lidzey3, Joseph Kuo-Hsiang Tang2 & Jason M. Smith1 Strong exciton–photon coupling is the result of a reversible exchange of energy between an excited state and a confined optical field. This results in the formation of polariton states that have energies different from the exciton and photon. We demonstrate strong exciton–photon coupling between light-harvesting complexes and a confined optical mode within a metallic optical microcavity. The energetic anti-crossing between the exciton and photon dispersions characteristic of strong coupling is observed in reflectivity and transmission with a Rabi splitting energy on the order of 150 meV, which corresponds to about 1,000 chlorosomes coherently coupled to the cavity mode. We believe that the strong coupling regime presents an opportunity to modify the energy transfer pathways within photosynthetic organisms without modification of the molecular structure. 1 Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK. 2 Department of Chemistry and Biochemistry, Clark University, Worcester, Massachusetts 01610-1477, USA. 3 Department of Physics & Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK. 4 Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK. 5 Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
    [Show full text]
  • Photosynthetic Light-Harvesting (Antenna) Complexes—Structures and Functions
    molecules Review Photosynthetic Light-Harvesting (Antenna) Complexes—Structures and Functions Heiko Lokstein 1,* , Gernot Renger 2,† and Jan P. Götze 3 1 Department of Chemical Physics and Optics, Charles University, Ke Karlovu 3, 12116 Prague, Czech Republic 2 Max-Volmer-Laboratorium, Technische Universität Berlin, Straße des 17. Juni 135, D-10623 Berlin, Germany 3 Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, D-14195 Berlin, Germany; [email protected] * Correspondence: [email protected] † Sadly, Professor Dr. Gernot Renger passed away on 12 January 2013. This article is dedicated to commemorate the outstanding contributions of Gernot Renger to oxygenic photosynthesis research. Abstract: Chlorophylls and bacteriochlorophylls, together with carotenoids, serve, noncovalently bound to specific apoproteins, as principal light-harvesting and energy-transforming pigments in photosynthetic organisms. In recent years, enormous progress has been achieved in the elucidation of structures and functions of light-harvesting (antenna) complexes, photosynthetic reaction centers and even entire photosystems. It is becoming increasingly clear that light-harvesting complexes not only serve to enlarge the absorption cross sections of the respective reaction centers but are vitally important in short- and long-term adaptation of the photosynthetic apparatus and regulation of the energy-transforming processes in response to external and internal conditions. Thus, the wide variety of structural diversity in photosynthetic antenna “designs” becomes conceivable. It is, however, common for LHCs to form trimeric (or multiples thereof) structures. We propose a simple, tentative explanation of the trimer issue, based on the 2D world created by photosynthetic membrane systems. Citation: Lokstein, H.; Renger, G.; Götze, J.P.
    [Show full text]
  • Open Hui Li Thesis.Pdf
    The Pennsylvania State University The Graduate School Eberly College of Science ORGANIZATION AND FUNCTION OF CHLOROSOME PROTEINS IN THE GREEN SULFUR BACTERIUM CHLOROBIUM TEPIDUM A Thesis in Biochemistry, Microbiology and Molecular Biology by Hui Li Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2006 ii The thesis of Hui Li has been reviewed and approved* by the following: Donald A. Bryant Ernest C. Pollard Professor of Biotechnology Professor of Biochemistry and Molecular Biology Thesis Advisor Chair of Committee John H. Golbeck Professor of Biochemistry and Biophysics Professor of Chemistry Teh-hui Kao Professor of Biochemistry and Molecular Biology Juliette T. J. Lecomte Associate Professor of Chemistry Robert A. Schlegel Professor of Biochemistry and Molecular Biology Head of the Department of Biochemistry and Molecular Biology * Signatures are on file in the Graduate School. iii ABSTRACT Chlorosomes are the light-harvesting antennae of the green sulfur bacteria, which usually live in extremely light-limited environments. Chlorosomes are sac-like structures with highly aggregated bacteriochlorophyll (BChl) c aggregates surrounded by a galactolipid/protein monolayer envelope. In the chlorosomes of Chlorobium tepidum, ten kinds of proteins (CsmA, CsmB, CsmC, CsmD, CsmE, CsmF, CsmH, CsmI, CsmJ, and CsmX) are located on the monolayer envelope membrane. Cross-linking experiments were performed to detect the relative locations and interactions among the chlorosome envelope proteins. The cross-linking reagent EDC (1-ethyl-3-(3- dimethylaminopropyl) carbodiimide) was used to cross-link the proteins of wild-type chlorosomes and chlorosomes from mutants lacking a single chlorosome protein, and the products were separated by SDS-PAGE and detected with antibodies against specific chlorosome proteins.
    [Show full text]
  • Comparison of the Physical Characteristics of Chlorosomes from Three Different Phyla of Green Phototrophic Bacteria
    Biochimica et Biophysica Acta 1827 (2013) 1235–1244 Contents lists available at ScienceDirect Biochimica et Biophysica Acta journal homepage: www.elsevier.com/locate/bbabio Comparison of the physical characteristics of chlorosomes from three different phyla of green phototrophic bacteria Peter G. Adams a, Ashley J. Cadby b, Benjamin Robinson b, Yusuke Tsukatani c, Marcus Tank c, Jianzhong Wen d,e, Robert E. Blankenship d,e, Donald A. Bryant c,f, C. Neil Hunter a,⁎ a Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK b Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK c Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA d Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA e Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA f Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA article info abstract Article history: Chlorosomes, the major antenna complexes in green sulphur bacteria, filamentous anoxygenic phototrophs, Received 9 April 2013 and phototrophic acidobacteria, are attached to the cytoplasmic side of the inner cell membrane and contain Received in revised form 5 July 2013 thousands of bacteriochlorophyll (BChl) molecules that harvest light and channel the energy to membrane- Accepted 8 July 2013 bound reaction centres. Chlorosomes from phototrophs representing three different phyla, Chloroflexus (Cfx.) Available online 16 July 2013 aurantiacus, Chlorobaculum (Cba.) tepidum and the newly discovered “Candidatus (Ca.) Chloracidobacterium (Cab.) thermophilum” were analysed using PeakForce Tapping atomic force microscopy (PFT-AFM).
    [Show full text]
  • Metabolism of Carbochidrates in the Cell of Green Photosintesis Sulfur Bacteria
    Chapter 10 Metabolism of Carbochidrates in the Cell of Green Photosintesis Sulfur Bacteria M. B. Gorishniy and S. P. Gudz Additional information is available at the end of the chapter http://dx.doi.org/10.5772/50629 1. Introduction Green bacteria - are phylogenetic isolated group photosyntetic microorganisms. The peculiarity of the structure of their cells is the presence of special vesicles - so-called chlorosom containing bacteriochlorofils and carotenoids. These microorganisms can not use water as a donor of electrons to form molecular oxygen during photosynthesis. Electrons required for reduction of assimilation CO2, green bacteria are recovered from the sulfur compounds with low redox potential. Ecological niche of green bacteria is low. Well known types of green bacteria - a common aquatic organisms that occur in anoxic, was lit areas of lakes or coastal sediments. In some ecosystems, these organisms play a key role in the transformation of sulfur compounds and carbon. They are adapted to low light intensity. Compared with other phototrophic bacteria, green bacteria can lives in the lowest layers of water in oxygen-anoxic ecosystems. Representatives of various genera and species of green bacteria differ in morphology of cells, method of movement, ability to form gas vacuoles and pigment structure of the complexes. For most other signs, including metabolism, structure photosyntetic apparats and phylogeny, these families differ significantly. Each of the two most studied families of green bacteria (Chlorobium families and Chloroflexus) has a unique way of assimilation of carbon dioxide reduction. For species of the genus Chlorobium typical revers tricarboxylic acids cycle, and for members of the genus Chloroflexus - recently described 3- hidrocsypropionatn cycle.
    [Show full text]
  • Investigation of the Bacteriochlorin Rings and Its Environment in Fenna
    Investigation of the Bacteriochlorin rings and its environment in Fenna-Matthews-Olsen antenna complex revealed by neutron and ultra-high resolution X-ray crystallography Brinda Selvaraja, Xun Lua, Matthew J. Cuneoa, Dean A.A. Mylesa a Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States Photosynthesis is initiated by the capture of a photon by a pigment in an antenna complex to form an exciton, followed by its transfer to the reaction center, where charge separation takes place. In green sulfur bacteria, Fenna-Matthews-Olson (FMO) protein functions as an energy transfer wire between chlorosome and reaction center. The efficiency of the energy transfer is mediated by the specific local environment around the pigments and their optimal geometry. To understand the efficient energy transfer designed by nature and be able to apply the knowledge to fabricating bio hybrid systems for light-harvesting, uncovering the atomic details of antenna complexes has been desirable. Here we report the neutron structure and the highest resolution X-ray structures (at cryogenic and room temperature) of FMO. We have crystallized FMO from Prosthecochloris. aestuarii in a new crystal form consisting of two FMO monomers in the asymmetric unit. Those monomers belong to two separate trimers, which show distinct occupancies for the eighth Bacteriochlorophyll (BChl). Large single crystals were obtained for room temperature neutron diffraction experiment, and an all-atom structure has been refined to 2.2 Å. The X-ray resolution has been improved to 0.99 Å for cryogenic temperature and 1.25 Å for room temperature, representing the highest resolution structures of FMO.
    [Show full text]